It is often desirable to obtain a record of the operation of a machine over a period of time. This is particularly true in the case of trucks and other motor vehicles where the record can be used to determine operating costs, to check operator performance, and to monitor the need for maintenance.
In the prior art, a chart recorder, usually connected to the drive train or transmission of a vehicle, has been used to create a graphical record of vehicle speed and distance traveled. Engine speed has also been recorded with this type of device. The chart recorder, however, has a number of serious drawbacks. Acceleration and deceleration information cannot be obtained from the chart at all, and the analog information which is on the chart can only be visually read thereby precluding any automatic data processing of the information.
Another type of prior art device is a magnetic tape recorder. While digital information on the resulting tape can be processed automatically, the devices which, are very costly, still do not record velocity information with sufficient accuracy to provide acceleration and deceleration information.